Jim Smart
October 14, 2005

In Part 1 of this story we introduced you to Ford's new-generation overhead cam Modular V-8 engines first introduced in 1991 in the Lincoln Town Car. We showed you the differences between Modular V-8 engines by explaining the variations between the Romeo, Michigan, and the Windsor, Ontario, engine plants. The differences are significant from one plant to the other, which affects interchangeability. This month, we're going to introduce you to Modular V-8 cylinder heads and their respective differences in our quest to teach you more about Ford's newest V-8 engine.

Choosing the right cylinder head for your SOHC or DOHC Modular V-8 boils down to understanding the differences between the two plants, and the pivotal year for performance: 1999. Ford improved the Modular V-8's cylinder heads that year on both the SOHC and DOHC engines.

SOHC Engines
It gets complicated when we get into cylinder heads for the 4.6L SOHC engines. To keep it simple, we will tell you there are two basic cylinder head designs: the Power Improved head casting from 1999-and-up and the dated round-port head from 1998-and-back. Ford calls it the non-PI head. We wish it were this simple in the real world of Modular V-8s, but it is a lot more involved in terms of interchangeability and design.

The '91-'92 Romeo SOHC head sports an F1AE casting number, with a bridge-style camshaft support bridge across the cam journals. These heads have no cam bearings. The camshafts ride right on the aluminum saddles (journals) in a cushion of engine oil under pressure. The cam covers sport nine bolt holes. There are two types of spark plug holes: short-reach and long-reach. Long-reach spark plugs indicate early castings. Later castings have a shorter-reach spark plug. This is important to remember whenever you're swapping heads.

The '93-'95 Romeo head castings have F2AE and F4AE casting numbers. All have short-reach spark plugs like later F1AE castings. Based on castings we have seen, provisions for the timing chain tensioner change on the '93-'95 head. So be mindful of this fact when you are swapping cylinder heads. In 1995, Ford changed the Romeo SOHC head castings again with a new casting number--F5AE--with a revised high-swirl combustion chamber. This casting would remain virtually the same until 1999, replaced by the PI head. Early castings had 51cc chambers with 146cc intake ports. These ports flow 156 cfm at .500-inch lift. This is not a performance head.

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When the Windsor foundry and engine plant came on line in 1996, so did a new crop of SOHC head castings designated primarily for trucks and large sport utilities. These castings are identified by F65E, F75, and F75E casting numbers until 1999. Cam covers are easily identified by 12 bolt holes instead of 9. Timing chain cover bolt-holes are also different on the Windsor heads--larger than the Romeo's. This means you have to stick with a Windsor timing cover when you are using Windsor heads. Again, Windsor everything, Romeo everything for simplicity and compatibility. The Windsor head has a high-swirl chamber like the F5AE Romeo head.

Beginning in 1999, Ford went to the Power Improved head at both Romeo and Windsor with the differences we have already addressed between the two plants. Look for a casting number of XL3E on this one, along with teardrop intake ports and heart-like 42cc combustion chambers. Intake port volume is 152 cc, flowing even more air at .500-inch valve lift. These heads are good for about 30 more horsepower if everything else is in place.

The Windsor PI head has separate cam journal caps. The Romeo PI head has the bridge-style caps mentioned earlier. This makes them easily identifiable at a glance. The Romeo head is the 1L2E casting. Timing chain cover bolt holes on the Romeo head are smaller (8 mm) than those we see on the Windsor heads (10 mm).

Ford Racing Performance Parts introduced a high-performance SOHC head in 1998. According to Sean Hyland of Sean Hyland Motorsport and author of How to Build Max-Performance 4.6 Liter Ford Engines (SA Designs PN SA82) , it's the best SOHC head produced to date. It has 51cc chambers, 173cc intake ports, and 206 cfm at .500-inch lift. The downside to the FRPP head is incompatibility with '99-and-up SOHC induction systems. It does, however, work well with '98-and-back induction systems.

DOHC Engines
The Modular V-8's greatest asset has long been the deep-breathing four-valve head. The way this head works is simple. There are two intake valves and two exhaust valves in each chamber. Below 3,000 rpm, we're on the primary port in the intake manifold, with the secondary butterflies closed. When we mash the throttle and open the secondaries, we're on both intake valves, taking full advantage of airflow. This was a good idea in theory, but in actual use, it didn't work very well in the beginning. Low- to mid-range torque was poor with these engines in normal driving, despite a big burst of power at high rpm at wide-open throttle.

Beginning in 1999, Ford went with the Tumble Port head. As its name implies, the Tumble Port tumbles the air and fuel as it rolls into the chamber, keeping fuel droplets in suspension. Not much changed aside from the shape of the chamber, which improved low- to mid-range torque. The 5.4L DOHC got its own kind of Tumble Head at the same time for use in the Lincoln Navigator.

Ford brought performance enthusiasts the FR500 four-valve head in 2002 from Ford Racing Performance Parts. Although mostly a racing cylinder head, it does have a purpose on the street--yielding as much as 7,000 rpm and a whopping 500 hp. Bolt these onto your DOHC and make as much as 50 more horsepower from the heads alone.

The FR500 head is similar to the '03 Cobra cylinder head, which was introduced with an Eaton supercharger. This head's intake ports flow 233 cfm at .500-inch valve lift. Exhaust ports yield 168 cfm. These factors make the '03-'04 Cobra head a popular head with performance buffs that love Mod motors. Mercury copped this head for the '03-'04 Marauder; ditto for Ford with the Mustang Mach 1 and Lincoln's Aviator.

Like the SOHC engine, the DOHC has twin camshafts with pressed-on lobes. The primary lobe profile is different than the secondary lobe profile. This means two different cam profiles for each engine: one for intake and one for exhaust. The aftermarket offers billet camshafts for the Ford DOHC.

So, which head is best for your 4.6L DOHC project? It can be safely said Ford has a healthy variety of factory DOHC castings that will work well for your four-valve project.

Timing Set
The 4.6 and 5.4 engines have two timing chains: one for each bank of cylinders, driven off two sprockets at the crankshaft. Each chain wraps around a large cam sprocket at each head. Chain tensioners on each bank of cylinders tension the chains. Chain tensioners create tension from engine oil pressure, with each chain following plastic chain guides. There are two basic kinds of chain guides: all-plastic and plastic with an aluminum support. There are two basic types of crankshaft timing gears: one-piece and two separate gears. The one-piece gear is actually two gears in one, which Ford went to in 2001. Ask for XR3Z-6306-BA at your Ford dealer. The earlier two-piece, two-gear setup is more prone to failure if you're going to rev it hard.

Confusion abounds with the Modular V-8 timing sets because there were so many changes along the way. Best we can tell from our research, there have been four basic timing sets for the SOHC engines. From 1991-'92, the Romeo engines had true roller chains, plastic guides (tensioners), and were marked left and right for easier installation. In 1993, there was a second Romeo timing set style, with different tensioners. From 1994-'99, Romeo opted for a link-style timing chain for quieter operation. This means different sprockets.

As you might expect by now, Windsor did its timing system differently than Romeo. First, the cam sprockets are permanently tied to the camshafts, which is unlike Romeo's bolt-on sprockets. The Windsor engines also had the link-style timing chains and sprockets for quieter operation. Tensioners were different than Romeo. Again, Romeo everything, Windsor everything when you're building a Mod motor.

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The Modular V-8 employs a camshaft unlike any you have ever seen in a vintage pushrod V-8. Instead of a single casting with machined lobes, the Mod motor has composite camshafts with hollow tubes and press-on lobes. The lobes are installed and indexed in a press-fit design. And because we have two cams inside the SOHC V-8, we have two different cam timing profiles for each bank. This means two cam part numbers for left and right. Camshaft profiles from 1991-'95 were pretty much the same from the factory.

Things changed in 1996, which is a pivotal year for the SOHC engines. From 1996-and-up, there are a greater variety of factory camshafts across Windsor and Romeo engines. The aftermarket offers a variety of cam profiles for these engines too. Just be mindful of your engine type and the cylinder heads used. It's also important to note Romeo SOHC engines have bolt-on cam sprockets, and Windsor SOHC engines have pressed-on cam sprockets.

From 1991-'98, the SOHC has .482-inch valve lift, with duration of 204/208 degrees intake/exhaust. With the PI heads in 1999, Ford went to .535-inch valve lift intake and .505-inch exhaust, with reduced durations of 192-degrees intake and 184-degrees exhaust. This approach improved low-end torque according to Sean Hyland. You may swap these cams into any SOHC engine without having to change springs.

Timing Chain Cover
From 1991-'92, expect to see 15 bolt holes in the Romeo F1AE/F2AE timing cover. From 1993-'95, Romeo timing covers keep the same-sized bolt holes (8 mm), but there's a location for the serpentine belt tensioner on the right-hand side. From 1996-'99, the timing cover changed again with the introduction of Windsor Mod motors. Expect to see casting numbers F6AE, F7AE, F7ZE, F8ZE. Windsor engines have larger bolt holes (10 mm); Romeo engines kept the 8mm bolt holes. Earlier timing covers will not interchange. The Mustang timing cover is different and unto itself. Expect to see yet a different timing cover casting number for Mustang GT 4.6 SOHC engines.

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Timing covers for the 1997-and-up F-150 and Expedition sport a F65E casting number, which means they're truck specific. Because these are Windsor engines, they have the larger 10mm bolt holes.

When Ford introduced the redesigned '99 Mustang, it also introduced a new timing cover--casting number XR3E. Serpentine belt tensioner positioning changed. That same year, the Econoline got the Mod motor, with its own timing cover--2L3E--that is identical to the truck timing cover sans the timing pointer. We don't know why.

Oil Pump
As you might expect, Ford took a completely different approach to lubrication with the Modular V-8. Instead of a cam-driven oil pump, the "gerotor" oil pump wraps around the front of the crankshaft, which provides a positive means of pump propulsion. A pickup tube extends deep into the oil pan from the pump at the front of the engine. This oil pump has a 12mm-wide rotor package that is larger in diameter than we are used to seeing with the older Ford V-8 designs. The factory gerotor package inside the pump is a powdered-metal design, just like the connecting rods. The downside to this approach is failure when we spin these rotors fast. The aftermarket offers us billet oil-pump gears, which perform more reliably than the factory gears. The DOHC uses the same basic oil pump as the SOHC, except for a wider gerotor package inside.

Because these engines run hotter with tighter tolerances, they have deep sump pans that hold nearly seven quarts of oil. Oil viscosities run much lower than we are used to with vintage Ford V-8s--5W20. Running anything heavier isn't healthy for the Modular V-8 because of its tight tolerances. The lower viscosity oil also creates less internal friction, which frees up power and improves efficiency.

The best factory oil pan is for the '96-'04 Mustang Cobra, which has scrapers and a baffled sump. This keeps plenty of oil around the pickup under all kinds of conditions. Of course, the greatest challenge is oil pan fit in vintage Fords. If you're going with a Mod motor in a classic Mustang, you will have to change the front end significantly and go with a Rod & Custom Motorsports, Heidt's, or other Mustang II style front end to make room for both engine and oil pan. There are also aftermarket front-sump pans that will fit vintage Fords with ease.

In the beginning, the 4.6 SOHC was equipped with a plastic intake manifold with an aluminum throttle body. With its long runners, this manifold helped the SOHC make good low- to mid-range torque. But it didn't set the world on fire in terms of real world power. For made this intake manifold out of plastic to keep the intake charge cooler. This manifold coincides with the early round-port heads used from 1991-'98. The '99-and-up PI heads use a different intake manifold designed for the PI ports.

One solid option for SOHC builders is the Ford Racing Performance Parts intake manifold that was introduced in 1998. This cast-aluminum manifold has long intake runners for a good combination of mid- and high-rpm torque. Instead of the single throttle body we see with most SOHC engines, the FRPP manifold has a twin-bore throttle body for increased air-flow. In 2001, Ford introduced a similar intake manifold for the Bullitt Mustang GT. Where it differs is its compatibility with the '99-and-up PI head. The earlier FRPP manifold will not work with the '99-and-up PI head.

Aftermarket cast-aluminum manifolds are available for the SOHC engines now. The downside to the stock plastic manifold is the inability to modify it in any way for improved performance, and its penchant for cracking with age or boosted environments.

The DOHC induction system is a two-port design where we operate on one primary intake port in normal driving, and open a series of secondary ports when the throttle is wide open. This is performed with an Intake Manifold Runner Control system (IMRC) that opens when the pedal hits the metal.

The '93-'98 Lincoln Mark VIII induction system had a twin-port design, where the primary intake port was different than the secondary intake port. This is likely the worst intake manifold you can use on top of a 4.6 DOHC engine because the intake runners are too small for high-rpm use.

If you have the early DOHC heads, you may opt for the '96-'98 Mustang Cobra intake manifold, a cast-aluminum affair with larger intake runners for improved breathing. It comes on stronger at high rpm. Not only are the runners larger, they are longer for improved low-end torque. When you mix in the improved IMRC, which is designed to come on at 3,200 rpm, this improves performance to some degree. There were actually two types of Cobra manifolds in 1998: plastic and aluminum. Opt for the cast manifold.

For those of you using the '99-and-up Tumble Port head, you need to use the appropriate intake manifold, also different from '99-and-up. If you happen to be running the super-rare '00 Cobra R head, you will need the Cobra R manifold as well.

Ignition System
The Modular V-8s have always had distributorless, computer-controlled ignition systems. From 1991-'98, they employed two coils packs--one located on each bank. The computer fires the spark plugs in pairs, with two spark plugs fired at the same time, but not igniting a fuel/air mix at the same time. This is known as a waste-spark system, where the computer's four channels fire two plugs at a time: one on compression-ignition stroke and the other on exhaust stroke. In 1999, Ford went to an eight-channel "coil-on-plug" ignition system, with each spark plug having its own ignition coil. This completely eliminates the ignition harness. With twin coil-pack ignition systems, each coil has four terminals to fire four spark plugs, with two of the terminals fired at a time in the four-channel systems.

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Fitment Issues
Likely the greatest challenge facing any of you considering a Mod' motor swap is size. The 4.6 SOHC and DOHC engines are larger than the rotund, hemi-head Boss 429 big-block. This presents serious challenges for anyone considering this engine swap. Because the 4.6 and 5.4 engines are considerably larger than the small- and even big-blocks we are used to, changes have to be made to some vintage Fords before these engines will fit.

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You may undertake special modifications to your compact or intermediate Ford's shock towers to make way for your 4.6 SOHC or DOHC engine; we have seen this performed in at least one classic Mustang. This, however, is not recommended. The best solution is to remove the shock towers and install a Mustang II or strut-based front suspension package to get the space to install a 4.6 or 5.4 in a vintage Ford intermediate or compact. This makes plenty of room for the wide-body V-8s. Another issue is weight. The 4.6 and 5.4 Modular V-8s weigh more than our small-blocks, but are on a par with vintage big-blocks weight wise. This will effect handling and weight distribution. The objective is to get these engines as close to the firewall as possible to help weight distribution. Modular V-8s all use the same engine mount, which keeps things simpler. Our goal is to undertake a Mod' motor swap in Mustang & Fords in the near future, learning as much as we can about fitment.

4.6 and 5.4 Weights
Engine Type Weight
4.6 SOHC 500 lbs
4.6 DOHC 425 lbs (al. block)
5.4 SOHC 525 lbs
5.4 DOHC 540 lbs

Engine Dimensions
Engine Height Depth Width
4.6 SOHC 26" 23 5/8" 26 5/8"
4.6 DOHC 27 1/8" 23 5/8" 26 5/8"
5.4 SOHC 28" 23 5/8" 27"
5.4 DOHC 35 1/2" 23 5/8" 28 1/4"

Bolt-On Necessities
According to Sullivan Performance, there are at least six different castings for the water outlet and oil filter mount. Sullivan suggests the F8ZZ-6881-AA outlet/mount because it accommodates an oil cooler. The Ford factory oil cooler is F8ZZ-6A64-2BA. Both are available from your Ford dealer for approximately $150 each at press time.